High Internal Quantum Efficiency Ultraviolet Emission from Phase-Transition Cubic GaN Integrated on Nanopatterned...

Area of Science:

• Materials Science
• Solid State Physics
• Optoelectronics

Background:

• Gallium nitride (GaN) is a crucial semiconductor for optoelectronic applications.
• Cubic GaN (c-GaN) offers different properties compared to hexagonal GaN (h-GaN).
• Achieving pure c-GaN phase and understanding its optical properties are key research areas.

Purpose of the Study:

• To investigate the ultraviolet (UV) emission characteristics of cubic GaN (c-GaN) obtained through a hexagonal-to-cubic phase transition.
• To understand the influence of substrate patterning and material growth on the phase purity and optical properties of c-GaN.
• To characterize the photonic properties, including emission polarization, decay time, and quantum efficiency, of phase-transition c-GaN.

Main Methods:

• Electron backscatter diffraction (EBSD) for phase purity analysis.
• Photoluminescence (PL) and cathodoluminescence (CL) for emission characteristics.
• Raman spectroscopy to study strain.
• Time-resolved photoluminescence (TRPL) for carrier dynamics.
• Temperature-dependent CL for internal quantum efficiency (IQE) and defect analysis.

Main Results:

• Substrate patterning and growth conditions impact c-GaN phase purity and UV emission.
• Raman spectroscopy indicated tensile strain in c-GaN.
• A c-GaN band edge emission decay time of 11 ps was measured via TRPL.
• UV emissions from both hexagonal and cubic GaN phases were linearly polarized.
• Room temperature IQE of ~29% was determined for phase-transition c-GaN.
• Intrinsic and extrinsic defect energy levels were found at ~124 meV and ~344 meV.
• A radiative lifetime of 38 ps was extracted using IQE and carrier decay lifetime.

Conclusions:

• Phase-transition c-GaN exhibits distinct UV emission characteristics influenced by fabrication parameters.
• The study provides detailed insights into the photonic properties and defect landscape of c-GaN.
• Understanding these properties is crucial for optimizing c-GaN in UV optoelectronic devices.